Circuit breaker



CIRCUIT BREAKER Filed July 7, 1950 Fig.l.

5| OFF .m r m m J 7 ll 8 i o nu 53' 46 2 5 39 7n6 0 6 7\ 4\ 5$ a G \P HET m I u wa 3 o 8 a 5 2 INVENTORS Eufene J. Walker and Me vinBingenheimer.

ATTORNEY Patented Sept. 18, 1951 CIRCUIT BREAKER Eugene J. Walker andMelvin Bingenheimer, Beaver, Pa., assignors to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication July '1, 1950, Serial No. 172,524

This invention relates to thermal circuit breakers forcontrollinglighting and moderate power circuits, and particularly toambient temperature compensation of the thermal trip device.

An object of the invention is to provide a circuit breaker embodying animproved thermally and magnetically responsive trip device including atemperature compensating trip member wherein the temperaturecompensating trip member and the magnetically responsive means aresupported entirely on the thermally responsive element.

Another object of the invention is to provide a circuit breakerembodying an improved thermally and magnetically responsive trip devicehaving the trip member and the magnetically responsive means supportedentirely on the'thermally responsive element wherein the trip membercomprises an ambient temperature compensating element.

Another object of the invention is to provide a circuit breakerembodying an improved trip device that is simple, reliable in operationand inexpensi e to manufacture.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to structure and operation, together withadditional objects and advantages thereof, will be best understood fromthe following detailed description thereof when read in conjunction withthe accompanying drawing.

In said drawing:

Figure 1 is a side elevational view, with the cover plate broken awayand partly in section, of a circuit breaker embodying the principles ofthe invention;

Fig. 2 is a fragmentary elevational view of the trip device showing thebimetal elements deflected in response to a predetermined rise inambient temperature.

Referring to Fig. l of the drawing, the circuit breaker comprisesgenerally, a housing H and a cover plate 13 therefor, most of which isshown broken away, both being constructed of molded insulating material,stationary contact means I5, movable contact means l1, an operatingmechanism I9 and a trip device 2|.

The stationary contact 15 is rigidly secured to the inner end of amulti-angular terminal member 23 which is seated in an angular slot 25molded in the housing H. The outer end of the terminal 23 is providedwith a connectingmeans 21 for connecting the terminal 23 in an electric9 Claims. (Cl. 20088) circuit. At the opposite end of the housing II isa terminal 29 which, at its inner end, supports the trip device 2| (tobe described later) and which is provided with a connecting means 3| atits outer end for connecting the terminal in an electric circuit.

The movable contact I1 is rigidly secured on the free end of a U-shapedswitch arm 31 having its legs 51 supported in recesses in the legs 55 ofa U-shaped operating lever 35 of molded insulating material. Theoperating lever 35 is pivotally supported by means of trunnions 41molded integral therewith and mounted in an opening in the housing H anda companion opening in the cover plate l3. An overcenter operatingspring 39 is connected under tension between the bight of the switch arm31 and a releasable carrier 33 pivoted on a pin 4| supported incompanion openings in the housing II and the cover plate The operatinglever 35 is provided with an integral operating handle 49 extendingthrough an opening 5i in the housing II. The operating lever is alsoprovided with an arcuate member 53 integral therewith cooperating withthe housing H to substantially close the opening 5| in all positions ofthe handle 49. The switch arm 31 is electrically connected by means of aflexible connection 59 to one end of a tripping bimetal element 45forming a part of the trip device 21 which is suitably secured,preferably by welding, to the inner end of the terminal 29.

The switch arm 31 is operated to manually open and close the contactmeans by manipulation of the handle 49. Movement of the handle in aclockwise direction carries the legs 51 of the switch arm 31 across tothe left of the line of action of the operating spring 39 which thenbiases switch arm to the open position and causes movement of the switcharm to the open position with a snap action.

The contacts are manually closed by reverse operation of the handle 49.Counterclcckwise movement of the handle 49 from the 01f position to theon position moves the legs 51 of the switch arm 31 across to the rightof the line of action of the operating spring 39 which, thereupon, actsto close the contacts with a snap action.

The circuit breaker is adapted to be tripped open instantaneously inresponse to overload currents above a predetermined value, or shortcircuit currents, and after a time delay in response to lesser overloadcurrents below the predetermined value by means of the trip device 2|.

. 3 Operation of the trip device 2| releases the carrier 33 whereuponthe overcenter spring 39 moves the carrier clockwise about pivot 4|,moving the line of action of the overcenter spring 39 to the right ofthe center line of the switch arm 37. The spring 39 then acts to movethe switch arm 31 to the open position with a snap action. The movementof the carrier 33 is arrested by its engagement with a projection 6|integral with the housing ll.

Before the contacts can be closed following an automatic operation, itis necessary to reset and relatch the mechanism. This is accomplished bymoving the handle 49 clockwise to the full off position during whichmovement the legs 55 of the operating lever 35 engage a pin 83 in thecarrier 33 and move the carrier counterclockwise about its pivot 4|.Near the end of the counterclockwise movement, the free end of thecarrier 33 wipes by a latch member 61, slightly flexing a compensatingbimetal element 69. Thereafter, the switch arm is moved to close thecontacts I-I'l, in the previously described manner, by movement of thehandle 49 counterclockwise to the on position.

The trip device 2! comprises the tripping bimetal element 45 connectedby means of the flexible connection 59 to the switch arm 31, the ambienttemperature compensating bimetal element 45, the latch member 61 and anelectroinagnet comprising a channel-shaped magnetic member 63 and amovable magnetic member 65. lhe terminal 29 is secured to the adjacentend wall of the housing II by means of a screw 'H and the trippingbimetal element 45 is rigidly secured by suitable means, such aswelding, to the upper inner end of the terminal 29. Just below the pointof attachment of the bimetal element 45 to the terminal 29 the bimetalelement 45 is formed inwardly at right angles and then downwardly for ashort distance substantially parallel to the terminal 29 to form a flatsurface to which the ambient temperature compensating bimetal element 69is secured. The compensating bimetal element 69 is secured to thetripping bimetal element 45 by welding or, as shown, by means of a rivet13. Below the point of connection of the compensating bimetal element 69to the tripping bimetal element 45, the latter extends downwardly at aslight angle to the terminal 29. The lower end of the compensatingbimetal 69 is looped as shown at 15 and the upwardly extending endthereof indicated at 16 carries an insulating button 11 for insulatingthe free end of the tripping bimetal element 45 from the free end of thecompensating bimetal 69.

The magnetic member 63, is rigidly mounted on and surrounds three sidesof the tripping bimetal element 45 and the magnetic member is rigidlysecured to the compensating-bimetal element 69 by means of a rivet 8|which also serves to secure the latch member 61 to the bimetal element69. As shown in the drawing, the latch member 61 normally engages andrestrains the-,carrier33 in operative position.

With normal rated current flowing through the tripping bimetal 45 themagnetic member 53 is not suihciently energized to attract the magneticmember 65. Upon the occurrence of, an

overload current above the rated current but.

below a predetermined value of, for instance 1000% of normal ratedcurrent, the tripping bimetal 45 is heated by the current flow thereinand deflects moving its free end toward the right. As the trippingbimetal deflects, it engages the insulating button I1 and moves thelower end of the compensating bimetal element 69 in the same directionand causes theslatch B1 to release the carrier 33 whereupon theoperating mechanism functions in the previously described manner toautomatically open the contacts.

Upon the occurrence of a heavy overload current on short circuit currentof, for example, 1000% or more of rated current, the current flowingthrough the tripping bimetal element 45 energizes the magnetic member 63sufiiciently to instantaneously attract and operate the armature 65which flexes the compensating bimetal element 69 toward the rightreleasing the carrier 33 and effecting substantially instantaneousopening of the breaker contacts.

The tripping bimetal 45 and the compensating bimetal 69 are electricallyinsulated from each other by an insulating element 19 disposedtherebetween at their point of attachment. The high expansion side ofthe tripping bimetal 45 is on the left and the high expansion side ofthe compensating bimetal 69 is on the right and on the inside of thelooped portion 15 thereof. Consequently, the bimetal element 45 and bodyof the bimetal B9 are disposed to deflect away from each other inresponse to an increase in ambient temperature, but, since the highexpansion side of the bimetal 69 is on the inside of the loop 15, thisportion of the bimetal 69 will tend to straighten out and the free endthereof, which carries the insulating button 11, will move toward theright -or in the same direction as the free end of the tripping bimetal45, thus allowing the tripping bimetal 45 to deflect slightly fartherbefore tripping. The trip device is shown in Fig. 2 with the bimetalelements 45 ad 69 deflected in response to. heating by a predeterminedrise in ambient temperature. It will be seen by reference to Fig. 2 thatthe vertical body of the compensating bimetal 69 has deflected slightlyto the left causing a slight increase in the latch overlap while thefree end 16 of the compensating bimetal 69 has deflected to the right anextent slightly greater than the deflection of the free end of thetripping bimetal 45. The thermal tripping time of the circuit breakerfor a given value of overload current will, therefore, be the sameregardless of changes in ambient temperature.

Adjusting means is provided whereby the tripping point of the thermaltrip may be varied without varying the magnetic air gap of the magneticmembers. The adjusting means comprises an adjusting screw threadedlyengaging the upper end of the terminal 29 and having its rounded headbearing against a concave seat in the housing II. An access opening 81in the housing I l permits the insertion of a suitable tool for turningthe screw 85 to thereby adjust the trip device. The opening 81 may besealed after adjustment to prevent tampering by unauthorized persons.

The invention provides a circuit breaker of few parts and simple andinexpensive construcmagnetic trip device and the compensating bimetalelement being mounted entirely on the tripping bimetal element. By thisconstruction the magnetic trip value is not affected by adjustment ofthe thermal trip element. By looping the free end of the compensatingbimetal around the free end of the tripping bimetal with thehigh-expansion sides of the bimetal elements facing each other andmounting the latch on the compensating bimetal, the free end of thecompensating bimetal element deflect in the same direction as the freeend of the tripping bimetal and the latch overlap is varied according tochanges in ambient temperature. This results in approximately the sametripping time for an overload current of given value regardless of thetemperature of the surrounding atmosphere.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes,structural details and arrangement of parts thereof may be made withoutdeparting from some of the essential features of the invention.

We claim as our invention:

1. A circuit breaker having relatively movable contact means andoperating mechanism therefor, a trip device comprising a bimetal tripelement having one end fixedly mounted and heated in response tothecurrent of the circuit, an ambient temperature responsive bimetalelement having one end rigidly mounted adjacent the fixedly mounted endof said current responsive bimetal element and extending along one sideof said current responsive bimetal element for compensating said currentresponsive bimetal element for changes in ambient temperature, one ofsaid bimetal elements having a portion disposed adjacent the other sideof the other of said bimetal elements, latch means on said ambienttemperature responsive bimetal element engaging and releasablyrestraining said operating mechanism, and said current responsivebimetal element deflecting when heated a predetermined amount inresponse to overload currents to operate said ambient temperatureresponsive bimetal element and cause said latch means to release saidoperating mechanism.

2. A circuit breaker having relatively movable contact means andoperating means therefor releasable to eilect automatic openin of saidcontact means, a trip device comprising a current responsive bimetaltrip element heated in response to the current of the circuit, anambient temperature responsive bimetal element carrying a latchingsurface and having its high expansion side disposed adjacent the highexpansion side of said current responsive bimetal trip element, saidambient temperature bimetal element having an abutment at the lowexpansion side of said current responsive bimetal element so that saidlatching surface and said am-- bient temperature bimetal element aremoved bodily by said current responsive bimetal trip element as itengages said abutment upon bending in response to overload currents.

3. A circuit breaker having relatively movable contact means and meansreleasable to efiect automatic opening of said contact means, a tripdevice comprising a current responsive bimetal element having one endrigidly supported, an ambient temperature responsive bimetal elementhaving one end rigidly supported on said current responsive bimetalelement adjacent the rigidly supported end thereof, said bimetalelements having their high expansion sides disposed adjacent each otherand said ambient temperature responsive bimetal element having anabutment disposed adjacent the low expansion side of said currentresponsive bimetal element, latch means on said ambient temperatureresponsive bimetal element releasably restraining said releasable means,said current responsive bimetal element deflecting when heated a predetermined amount in response to overload currents to engage saidabutment and flex said ambient temperature responsive bimetal element tocause said latch means to release said releasable means.

4. A circuit breaker having relatively movable contact means and meansreleasable to effect automatic opening of said contact means, a tripdevice comprising a current responsive bimetal element having one endrigidly supported, an ambient temperature responsive bimetal elementhaving one end rigidly supported on said current responsive bimetalelement adjacent the rigidly supported end thereof, said bimetal elements having their high expansion sides disposed adjacent each other andsaid ambient temperature responsive bimetal element having an abutmentdisposed adjacent the low expansion side of said current responsivebimetal element, latch means on said ambient temperature responsivebimetal element releasably restraining said releasable means, saidcurrent responsive bimetal element deflecting when heated apredetermined amount in response to overload currents below apredetermined value to engage said abutment and flex said ambienttemperature responsive bimetal element to cause said latch means torelease said releasable means, electroresponsive means comprising a pairof magnetic members one mounted on said current responsive bimetalelement and the other mounted on said ambient temperature responsivebimetal element, said electroresponsive means being energized inresponse to overload currents above said predetermined value to flexsaid ambient temperature responsive bimetal and cause said latch meansto instantaneously release said releasable means.

5. A circuit breaker including relatively movable contacts, a releasablemember operable when released to effect opening of said contacts, tripmeans including a circuit responsive bimetal element electricallyconnected to be traversed by current, electroresponsive means comprisinga pair of magnetic members on opposite sides of said current responsivebimetal element, one of said magnetic members being mounted on saidcurrent responsive bimetal element and energized by current flowtherethrough, both of said magnetic members being movable, an ambienttemperature responsive bimetal element for compensating said currentresponsive bimetal element for changes in ambient temperature and havinga portion thereof movable to effect release of said releasable member,one of said bimetal elements having an abutment disposed adjacent thelow expansion side of the other of said bimetal elements the other ofsaid magnetic members being mounted on said ambient temperatureresponsive bimetal element and movable magnetically toward said onemagnetic member and causing bending movement of said ambient temperatureresponsive bimetal element against its normal bias to the point wheresaid portion of said ambient temperature responsive bimetal elementcauses release of said releasable member, said other magnetic memberbeing movable upon thermal bending of said current responsive bimetalelement and said bending of said current responsive bimetal also causingmovement of said portion of said ambient temperature responsive bimetalelement to release said releasable member.

6. In a circuit breaker having relatively movable contacts and a memberreleasable to effect opening of said contacts, a trip device foreffecting release of said releasable member comprising a currentresponsive bimetal element, an ambient temperature responsive bimetalelement having one and rigidly secured to one side of said currentresponsive bimetal element and having its free end formed to engage theopposite side of said current responsive bimetal element, the highexpansion side of said bimetal elements being disposed adjacent eachother to compensate said trip device for changes in ambient temperature,latch means on said ambient temperature responsive bimetal elementnormally restraining said releasable member against operation, saidcurrent responsive bimetal element when heated a predetermined amount inresponse to' overload currents below a predetermined value moving saidambient temperature responsive bimetal element to cause release of saidreleasable member, and electroresponsive means supported by said currentresponsive bimetal element and operable when energized in response tooverload currents above said predetermined value to flex said ambienttemperature bimetal element against its normal bias and instantaneouslyrelease said releasable member.

7. In an automatic electric circuit breaker having separable contactmeans and means releasable to effect separation of said contacts,current responsive means for effecting release of said releasable meansupon passage of an overload current through said circuit breakercomprising a current responsive bimetallic member heated in response tothe flow of current through said breaker, a magnetic yoke supported uponsaid current responsive bimetallic member and energized in response tothe flow of current through said breaker, an armature member alsosupported upon said current responsive bimetallic member and adapted tobe attracted to said yoke upon the occurrence of an overload current ofsuificient value, an ambient temperature responsive bimetallic elementfor compensating said current responsive bimetalic element for changesin ambient temperature, said ambient temperature responsive bimetallicelement having a latching surface engageable by said releasable means, amain portion of said ambient temperature responsive bimetallic elementbeing disposed on the high expansion side of said current responsivebimetallic element and having an abutment at the low expansion side ofsaid current responsive bimetallic element so that the latching surfaceand said ambient temperature responsive bimetallic element are movedbodily by said current responsive bimetallic element as it engages saidabutment upon flexing in response to the passage of moderate overloadcurrents, said armature moving said latching surface and said ambienttemperature responsive bimetallic element relative to said current responsive bimetallic element as said armature is attracted in response toheavy overload and short bimetal element and having an abutment at thelow expansion side of said current responsive bimetal element so thatsaid latching surface and said ambient temperature responsive bimetalelement are moved bodily by said current responsive bimetal element asit engages said abutment upon bending in response to overload currents,and said ambient temperature responsive bimetal element upon bendingthereof in response to changes in ambient temperatures moving saidlatching surface relative to said releasable means and moving saidabutment relative to the current responsive bimetal element tocompensate for changes in ambient temperatures.

9. A circuit breaker having relatively movable contact means and meansreleasable to effect automatic opening of said contact means, a tripdevice comprising a current responsive bimetal element having one endrigidly supported, an ambient temperature responsive bimetal elementhaving one end rigidly supported adjacent the rigidly supported end ofsaid current responsive bimetal element, said bimetal elements havingtheir high expansion sides disposed adjacent each other, latch means onsaid ambient temperature responsive bimetal element releasablyrestraining said releasable means, one of said bimetal elements havingan extension thereon cooperating with the low expansion side of theother of said bimetal elements so that thermal bending of the currentresponsive bimetal element causes flexing of said ambient temperatureresponsive bimetal element and release of said releasable means.

EUGENE J. WALKER. MELVIN BINGENHEIMER.

REFERENCES CITED FOREIGN PATENTS Country Date Germany July 20, 1935Number

